Inteins are unique protein insertion sequences capable of self-excision, enabling the covalent ligation of flanking extein peptides via amide bond formation. This process proceeds spontaneously without requiring external enzymes, cofactors, or chemical reagents, granting inteins exceptional biocompatibility and traceless performance in protein engineering applications. Split inteins represent a specialized and versatile subclass whose splicing domains are encoded by two separate gene fragments rather than a single continuous open reading frame. These fragments, known as the N-terminal (IntN) and C-terminal (IntC) split inteins, associate through non-covalent interactions including hydrophobic forces, hydrogen bonds, and van der Waals forces to assemble into an active three-dimensional structure, which then drives efficient extein ligation and enables protein trans-splicing. Protein trans-splicing mediated by split inteins has become a cornerstone for traceless protein ligation owing to its high specificity and irreversibility, fundamentally reshaping strategies for protein modification, assembly, and functional regulation. Compared with traditional chemical ligation methods, split intein systems require no complex chemical derivatization of peptide fragments and can operate efficiently at micromolar concentrations under physiological conditions, thus avoiding structural and functional damage caused by organic reagents. In contrast to enzymatic ligation tools such as sortase, split inteins eliminate the need for additional enzymes or cofactors, simplifying reaction systems, reducing costs, and minimizing non-specific side products. These distinctive advantages render split inteins highly promising for applications in chemical biology, synthetic biology, and biopharmaceutical development. In recent years, deepened mechanistic understanding has established structure-guided rational design as the primary approach to overcoming key limitations of split inteins, including intrinsic aggregation propensity, strict extein sequence dependence, and limited splicing efficiency. Bioinformatic tools have been used to identify aggregation-prone regions in the IntN fragment, and site-directed mutagenesis of hydrophobic residues, relocation of split sites, or removal of misfolding-prone sequences has substantially reduced in vitro aggregation and improved soluble expression and assembly activity. Rational engineering of catalytic residues and adjacent flexible loops has relaxed strict amino acid preferences at extein junctions, enhancing sequence tolerance and reducing the risk of functional impairment in target proteins. Consensus design based on multiple sequence alignments has yielded ultra-fast splicing variants such as Cfa DnaE and Cat-TerL, which exhibit significantly accelerated kinetics and improved tolerance to denaturing conditions. Meanwhile, advances in structural biology have further clarified the conformational dynamics and catalytic mechanisms of splicing, supporting the precise design of high-performance intein modules. On this basis, electrostatic interaction tuning and metagenomic screening have yielded multiple mutually orthogonal split intein pairs, enabling selective multi-fragment protein ligation and providing new routes for the efficient synthesis of large multi-domain functional proteins. With these engineered split inteins offering continuously improved performance and expanded applicability, protein trans-splicing has been widely applied in numerous cutting-edge areas of protein research and biomedicine. In gene delivery, split intein-based systems overcome the packaging limit of adeno-associated viral vectors, enabling the accurate reconstitution of large therapeutic proteins and base editors in target cells, thereby enhancing the efficacy and scope of gene therapy for genetic diseases. In internal protein sequence editing, split inteins mediate precise sequence replacement and modification in flexible regions or loops of target proteins, without the need for complex multi-step ligation and protein refolding involved in traditional protein semisynthesis. In protein-protein interaction studies, intein-mediated splicing covalently captures transient and weak intracellular complexes, enabling sensitive, high-throughput interaction detection and drug screening. In synthetic biology, conditionally controllable splicing systems support the construction of diverse intracellular and cell-surface biological logic gates for the precise regulation of cellular behavior. In mechanistic biochemical research, split inteins enable photocatalytic proximity labeling and site-specific tagging, allowing the preparation of homogeneous protein samples carrying precise post-translational modifications such as ubiquitination and polyglutamylation for chromatin interactome analysis and epigenetic studies. Moreover, covalent trapping strategies using split inteins stabilize transient enzymatic intermediates, providing unprecedented insights into molecular mechanisms such as nucleosome ubiquitination that are difficult to elucidate using conventional methods. This review systematically summarizes key technological advances in split inteins over the past decade, highlighting engineering strategies, mechanistic insights, and the development of orthogonal components. It comprehensively surveys emerging applications at the frontiers of protein research, analyzes current core challenges, and proposes future directions, particularly emphasizing artificial intelligence-driven de novo design and novel splicing pathways to break existing technical bottlenecks. By enabling traceless, efficient, and versatile protein manipulation, split inteins continue to serve as indispensable tools that drive innovation in protein engineering and fundamental life science research.

Tacit knowledge of tongue inspection is content that affects diagnostic results but is difficult to be explicit. Its cognitive characteristics are rooted in xiang thinking and embodiment. It constructs multidimensional associations between tongue manifestations and disease mechanisms through imagery mapping， and it relies on the practitioner's bodily perception， clinical context， and long-term practice for continuous internalization. In response to the neglect of tacit transmission and individual cognitive processes in current traditional Chinese medicine （TCM） tacit knowledge research， an empirical research framework integrating cognitive neuroscience is proposed. Specifically， event-related potential （ERP） and eye tracking （ET） technologies can be used to capture the brain electrical activity and eye movement trajectories of experts and novices in different tongue diagnosis cognitive tasks. By integrating multimodal cognitive data such as behaviorism， ERP components， and ET indicators， the implicit cognitive advantages of experts in the perception， mapping， and decision-making stages of tongue diagnosis are presented， and the possibility of achieving tacit knowledge transformation through visual cognitive transfer training is explored. Exploring empirical pathways to uncover the cognitive mechanisms of tongue diagnosis tacit knowledge is of great significance for the inheritance of traditional Chinese medicine.

GPR126, also known as ADGRG6, is one of the most deeply studied aGPCRs. Initially, GPR126 was thought to be a receptor associated with muscle development and was primarily expressed in the muscular and skeletal systems. With the deepening of research, it was found that GPR126 is expressed in multiple mammalian tissues and organs, and is involved in many biological processes such as embryonic development, nervous system development, and extracellular matrix interactions. Compared with other aGPCRs proteins, GPR126 has a longer N-terminal domain, which can bind to ligands one-to-one and one-to-many. Its N-terminus contains five domains, a CUB (complement C1r/C1s, Uegf, Bmp1) domain, a PTX (Pentraxin) domain, a SEA (Sperm protein, Enterokinase, and Agrin) domain, a hormone binding (HormR) domain, and a conserved GAIN domain. The GAIN domain has a self-shearing function, which is essential for the maturation, stability, transport and function of aGPCRs. Different SEA domains constitute different GPR126 isomers, which can regulate the activation and closure of downstream signaling pathways through conformational changes. GPR126 has a typical aGPCRs seven-transmembrane helical structure, which can be coupled to Gs and Gi, causing cAMP to up- or down-regulation, mediating transmembrane signaling and participating in the regulation of cell proliferation, differentiation and migration. GPR126 is activated in a tethered-stalk peptide agonism or orthosteric agonism, which is mainly manifested by self-proteolysis or conformational changes in the GAIN domain, which mediates the rapid activation or closure of downstream pathways by tethered agonists. In addition to the tethered short stem peptide activation mode, GPR126 also has another allosteric agonism or tunable agonism mode, which is specifically expressed as the GAIN domain does not have self-shearing function in the physiological state, NTF and CTF always maintain the binding state, and the NTF binds to the ligand to cause conformational changes of the receptor, which somehow transmits signals to the GAIN domain in a spatial structure. The GAIN domain can cause the 7TM domain to produce an activated or inhibited signal for signal transduction, For example, type IV collagen interacts with the CUB and PTX domains of GPR126 to activate GPR126 downstream signal transduction. GPR126 has homology of 51.6%-86.9% among different species, with 10 conserved regions between different species, which can be traced back to the oldest metazoans as well as unicellular animals.In terms of diseases, GPR126 dysfunction involves the pathological process of bone, myelin, embryo and other related diseases, and is also closely related to the occurrence and development of malignant tumors such as breast cancer and colon cancer. However, the biological function of GPR126 in various diseases and its potential as a therapeutic target still needs further research. This paper focuses on the structure, interspecies differences and conservatism, signal transduction and biological functions of GPR126, which provides ideas and references for future research on GPR126.

BACKGROUND:Osteoporotic fracture is the most serious complication of osteoporosis.Previous studies have demonstrated that gut microbiota has a regulatory effect on skeletal tissue and that gut microbiota has an important relationship with osteoporotic fracture,but the causal relationship between the two is unclear. OBJECTIVE:To explore the causal relationship between gut microbiota and osteoporotic fractures using Mendelian randomization method. METHODS:The genome-wide association study(GWAS)datasets of gut microbiota and osteoporotic fracture were obtained from the IEU Open GWAS database and the Finnish database R9,respectively.Using gut microbiota as the exposure factor and osteoporotic fracture as the outcome variable,Mendelian randomization analyses with random-effects inverse variance weighted,MR-Egger regression,weighted median,simple model,and weighted model methods were performed to assess whether there is a causal relationship between gut microbiota and osteoporotic fracture.Sensitivity analyses were performed to test the reliability and robustness of the results.Reverse Mendelian randomization analyses were performed to further validate the causal relationship identified in the forward Mendelian randomization analyses. RESULTS AND CONCLUSION:The results of this Mendelian randomization analysis indicated a causal relationship between gut microbiota and osteoporotic fracture.Elevated abundance of Actinomycetales[odds ratio(OR)=1.562,95%confidence interval(CI):1.027-2.375,P=0.037),Actinomycetaceae(OR=1.561,95%CI:1.027-2.374,P=0.037),Actinomyces(OR=1.544,95%CI:1.130-2.110,P=0.006),Butyricicoccus(OR=1.781,95%CI:1.194-2.657,P=0.005),Coprococcus 2(OR=1.550,95%CI:1.068-2.251,P=0.021),Family ⅩⅢ UCG-001(OR=1.473,95%CI:1.001-2.168,P=0.049),Methanobrevibacter(OR=1.274,95%CI:1.001-1.621,P=0.049),and Roseburia(OR=1.429,95%CI:1.015-2.013,P=0.041)would increase the risk of osteoporotic fractures in patients.Elevated abundance of Bacteroidia(OR=0.660,95%CI:0.455-0.959,P=0.029),Bacteroidales(OR=0.660,95%CI:0.455-0.959,P=0.029),Christensenellacea(OR=0.725,95%CI:0.529-0.995,P=0.047),Ruminococcaceae(OR=0.643,95%CI:0.443-0.933,P=0.020),Enterorhabdus(OR=0.558,95%CI:0.395-0.788,P=0.001),Eubacterium rectale group(OR=0.631,95%CI:0.435-0.916,P=0.016),Lachnospiraceae UCG008(OR=0.738,95%CI:0.546-0.998,P=0.048),and Ruminiclostridium 9(OR=0.492,95%CI:0.324-0.746,P=0.001)would reduce the risk of osteoporotic fractures in patients.We identified 16 gut microbiota associated with osteoporotic fracture by the Mendelian randomization method.That is,using gut microbiota as the exposure factor and osteoporotic fracture as the outcome variable,eight gut microbiota showed positive causal associations with osteoporotic fracture and another eight gut microbiota showed negative causal associations with osteoporotic fracture.The results of this study not only identify new biomarkers for the early prediction of osteoporotic fracture and potential therapeutic targets in clinical practice,but also provide an experimental basis and theoretical basis for the study of improving the occurrence and prognosis of osteoporotic fracture through gut microbiota in bone tissue engineering.

BackgroundGraduate students frequently face life events， many of which may adversely affect their mental well-being. However， the interaction between life events and the development of depression， anxiety， and somatic symptoms remains unclear. ObjectiveTo explore the relationship between life events and the development of depressive， anxiety and somatic symptoms in graduate students， thereby informing prevention strategies for these conditions. MethodsA sample of 6 722 newly enrolled graduate students at a comprehensive university in Southwest China from September to November 2018 was selected. The assessment was conducted using the Adolescent Self-rating Life Events Checklist （ASLEC）， the 7-item Generalized Anxiety Disorder scale-7 item （GAD-7）， the Patient Health Questionnaire Depression Scale-9 item （PHQ-9）， and the Patient Health Questionnaire-15 （PHQ-15）. Network analysis was implemented by using the bootnet and qgraph packages in the R software （version 4.2.3）， with centrality indices calculated to identify core and bridge symptoms within the network. ResultsThe study encompassed a total of 6 171 graduate students， representing 91.80% of the target population. The prevalence rates of anxiety， depressive， and somatic symptoms among graduate students were 12.59% （777/6 171）， 16.63% （1 026/6 171）， and 27.66% （1 707/6 171）， respectively. Network analysis revealed that 'academic stress' was the core symptom with the highest strength and expected influence （both values=1.207）， while 'feeling down， depressed， or hopeless' was the bridge symptom with the highest bridge strength and bridge expected influence （both values=0.454）. There was no significant difference in global network strength and edge weight between women and men （P>0.05）. ConclusionAcademic stress， emerging as the core symptom， assumes a dominant position within the symptom network and exhibits strong interactions with other negative affective states. There was no gender difference in the network structure.

Neurodevelopmental disorders (NDDs), including autism spectrum disorder (ASD), attention deficit hyperactivity disorder (ADHD), and intellectual developmental disorder (IDD), are highly prevalent and lack effective treatments, posing significant health challenges. These disorders are frequently comorbid with disruptions in sleep rhythms, and sleep-related indicators are often used to assess disease severity and treatment efficacy. Recent evidence has highlighted the crucial roles of circadian rhythm disturbances and circadian clock gene mutations in the pathogenesis of NDDs. This review focuses on the mechanisms by which circadian rhythm disruptions and circadian clock gene mutations contribute to cognitive, behavioral, and emotional disorders associated with NDDs, particularly through the dysregulation of dopamine system. Additionally, we discussed the potential of targeting the circadian system as novel therapeutic strategies for the treatment of NDDs.
Humans ; Neurodevelopmental Disorders/genetics* ; Attention Deficit Disorder with Hyperactivity/genetics* ; Circadian Rhythm/genetics* ; Autism Spectrum Disorder/genetics* ; Mutation ; Intellectual Disability/genetics* ; Circadian Clocks/physiology* ; Dopamine/metabolism*

ObjectiveIn the realm of forensic science, dust is a valuable type of trace evidence with immense potential for intricate investigations. With the development of DNA sequencing technologies, there is a heightened interest among researchers in unraveling the complex tapestry of microbial communities found within dust samples. Furthermore, striking disparities in the microbial community composition have been noted among dust samples from diverse geographical regions, heralding new possibilities for geographical inference based on microbial DNA analysis. The pivotal role of microbial community data from dust in geographical inference is significant, underscoring its critical importance within the field of forensic science. This study aims to delve deeply into the nuances of fungal community composition across the urban landscapes of Beijing, Fuzhou, Kunming, and Urumqi in China. It evaluates the accuracy of biogeographic inference facilitated by the internal transcribed spacer 2 (ITS2) fungal sequencing while concurrently laying a robust foundation for the operational integration of environmental DNA into geographical inference mechanisms. MethodsITS2 region of the fungal genomes was amplified using universal primers known as 5.8S-Fun/ITS4-Fun, and the resulting DNA fragments were sequenced on the Illumina MiSeq FGx platform. Non-metric multidimensional scaling analysis (NMDS) was employed to visually represent the differences between samples, while analysis of similarities (ANOSIM) and permutational multivariate analysis of variance (PERMANOVA) were utilized to statistically evaluate the dissimilarities in community composition across samples. Furthermore, using Linear Discriminant Analysis Effect Size (LEfSe) analysis to identify and filter out species that exhibit significant differences between various cities. In addition, we leveraged SourceTracker to predict the geographic origins of the dust samples. ResultsAmong the four cities of Beijing, Fuzhou, Kunming and Urumqi, Beijing has the highest species richness. The results of species annotation showed that there were significant differences in the species composition and relative abundance of fungal communities in the four cities. NMDS analysis revealed distinct clustering patterns of samples based on their biogeographic origins in multidimensional space. Samples from the same city exhibited clear clustering, while samples from different cities showed separation along the first axis. The results from ANOSIM and PERMANOVA confirmed the significant differences in fungal community composition between the four cities, with the most pronounced distinctions observed between Fuzhou and Urumqi. Notably, the biogeographic origins of all known dust samples were successfully predicted. ConclusionSignificant differences are observed in the fungal species composition and relative abundance among the cities of Beijing, Fuzhou, Kunming, and Urumqi. Employing fungal ITS2 sequencing on dust samples from these urban areas enables accurate inference of biogeographical locations. The high feasibility of utilizing fungal community data in dust for biogeographical inferences holds particular promise in the field of forensic science.

ObjectiveTo explore the mechanism of the anti-cancer compound formula Feiyanning in inhibiting epithelial-mesenchymal transition （EMT） and invasion and metastasis of non-small cell lung cancer （NSCLC）. MethodsCell proliferation and activity were assessed using the cell counting kit-8（CCK-8） assay to evaluate the effect of Feiyanning on the proliferation of A549 and H1299 cells. Wound healing and Transwell assays were conducted to examine Feiyanning's impact on the metastasis of A549 and H1299 cells. The effects of Feiyanning on EMT and the transforming growth factor-β₁ （TGF-β₁）/Smad signaling pathway proteins in A549 and H1299 cells were detected by Western blot. Exogenous TGF-β₁ was used to induce EMT in A549 and H1299 cells. The effects of Feiyanning on TGF-β₁-induced NSCLC cell metastasis， EMT， and the TGF-β₁/Smad pathway proteins were assessed by wound healing assay， Transwell assay， and Western blot. In vivo， an A549 lung metastasis model was established via tail vein injection in nude mice. A total of 28 SPF male nude mice were randomly divided into four groups： Model （NC） group， Feiyanning low-dose （FYN1） group， Feiyanning high-dose （FYN2） group， and the positive control group （TGF-β receptor kinase inhibitor SB431542 group）. The corresponding interventions were performed. After 40 days， the mice were euthanized， and lung metastases were analyzed. The expression of E-cadherin， N-cadherin， p-Smad2， and p-Smad3 in each group was detected by immunohistochemistry （IHC）. ResultsAfter Feiyanning intervention， compared to the blank group， Feiyanning inhibited the proliferation of A549 and H1299 cells in a concentration-dependent manner （P<0.01）. The metastasis ability of Feiyanning-treated cells was significantly decreased compared to the blank group （P<0.01）. The expression of EMT marker proteins N-cadherin and zinc finger transcription factors （Zeb1， Snail， Slug） was significantly reduced in the Feiyanning groups compared to the blank group （P<0.05， P<0.01）. The expression of p-Smad2/3， Smad2/3， TβRI， and TβRⅡ， key proteins in the TGF-β₁/Smad signaling pathway， was also significantly decreased （P<0.01）. In the TGF-β₁-induced EMT model， compared to the TGF-β₁ group， the cell metastasis ability in the Feiyanning groups was reduced （P<0.01）， and the expression levels of N-cadherin， Zeb1， Snail， and Slug were significantly lower （P<0.01）. The expression levels of p-Smad2/3， Smad2/3， TβRI， and TβRⅡ were also significantly reduced （P<0.01）. In vivo results showed that compared to the model group， the number of lung metastases in the FYN1， FYN2， and SB431542 groups was reduced （P<0.01）， and the range of cell infiltration was narrowed. Immunohistochemical results showed that compared to the model group， the expression of E-cadherin in the FYN1， FYN2， and SB431542 groups was increased （P<0.01）， the expression of N-cadherin decreased （P<0.05， P<0.01）， and the expression of p-Smad2 and p-Smad3， key proteins of the TGF-β₁/Smad pathway， was reduced （P<0.01）. ConclusionFeiyanning inhibits the invasion and metastasis of NSCLC cells and EMT. The mechanism is related to the inhibition of TGF-β₁/Smad signaling pathway.

ObjectiveTo explore the mechanism of the anti-cancer compound formula Feiyanning in inhibiting epithelial-mesenchymal transition （EMT） and invasion and metastasis of non-small cell lung cancer （NSCLC）. MethodsCell proliferation and activity were assessed using the cell counting kit-8（CCK-8） assay to evaluate the effect of Feiyanning on the proliferation of A549 and H1299 cells. Wound healing and Transwell assays were conducted to examine Feiyanning's impact on the metastasis of A549 and H1299 cells. The effects of Feiyanning on EMT and the transforming growth factor-β₁ （TGF-β₁）/Smad signaling pathway proteins in A549 and H1299 cells were detected by Western blot. Exogenous TGF-β₁ was used to induce EMT in A549 and H1299 cells. The effects of Feiyanning on TGF-β₁-induced NSCLC cell metastasis， EMT， and the TGF-β₁/Smad pathway proteins were assessed by wound healing assay， Transwell assay， and Western blot. In vivo， an A549 lung metastasis model was established via tail vein injection in nude mice. A total of 28 SPF male nude mice were randomly divided into four groups： Model （NC） group， Feiyanning low-dose （FYN1） group， Feiyanning high-dose （FYN2） group， and the positive control group （TGF-β receptor kinase inhibitor SB431542 group）. The corresponding interventions were performed. After 40 days， the mice were euthanized， and lung metastases were analyzed. The expression of E-cadherin， N-cadherin， p-Smad2， and p-Smad3 in each group was detected by immunohistochemistry （IHC）. ResultsAfter Feiyanning intervention， compared to the blank group， Feiyanning inhibited the proliferation of A549 and H1299 cells in a concentration-dependent manner （P<0.01）. The metastasis ability of Feiyanning-treated cells was significantly decreased compared to the blank group （P<0.01）. The expression of EMT marker proteins N-cadherin and zinc finger transcription factors （Zeb1， Snail， Slug） was significantly reduced in the Feiyanning groups compared to the blank group （P<0.05， P<0.01）. The expression of p-Smad2/3， Smad2/3， TβRI， and TβRⅡ， key proteins in the TGF-β₁/Smad signaling pathway， was also significantly decreased （P<0.01）. In the TGF-β₁-induced EMT model， compared to the TGF-β₁ group， the cell metastasis ability in the Feiyanning groups was reduced （P<0.01）， and the expression levels of N-cadherin， Zeb1， Snail， and Slug were significantly lower （P<0.01）. The expression levels of p-Smad2/3， Smad2/3， TβRI， and TβRⅡ were also significantly reduced （P<0.01）. In vivo results showed that compared to the model group， the number of lung metastases in the FYN1， FYN2， and SB431542 groups was reduced （P<0.01）， and the range of cell infiltration was narrowed. Immunohistochemical results showed that compared to the model group， the expression of E-cadherin in the FYN1， FYN2， and SB431542 groups was increased （P<0.01）， the expression of N-cadherin decreased （P<0.05， P<0.01）， and the expression of p-Smad2 and p-Smad3， key proteins of the TGF-β₁/Smad pathway， was reduced （P<0.01）. ConclusionFeiyanning inhibits the invasion and metastasis of NSCLC cells and EMT. The mechanism is related to the inhibition of TGF-β₁/Smad signaling pathway.